As a contract standoff between AT&T and 21,000 unionized workers in its mobile business drags into a eighth month, the employees are trying to increase political pressure on the carrier.

So far, 255 state and local politicians have sent letters to AT&T CEO Randall Stephenson backing the workers, the Communications Workers of America union says. Among the senders are six Democratic senators and numerous members of California’s delegation in the House of Representatives.

“While we are aware of the changes that have taken place in the telecommunications industry, we know that AT&T wireless workers are the driving force behind your most profitable division,” 12 members of the Arizona House of Representatives wrote to Stephenson in one recent letter. “They deserve to share in the company’s success and growth.”

Still, AT&T does not appear moved by the campaign or earlier moves by the mobile workers in 36 states and Washington, D.C., including a protest outside Apple headquarters for the debut of new iPhones last month and a short strike in May that forced many wireless stores to close for a weekend.

Although the workers have concerns about wages, health benefits, and other issues, job security and sales commission rates appear to be at the center of the dispute. To highlight the issue of call center jobs being outsourced to foreign countries, some AT&T workers traveled to the Dominican Republic in early May to meet with their counterparts there who now handle AT&T customer service calls.

AT&T said on Friday that it has been in touch with the letter writers and plans to continue to bargain with the workers, whose contract expired in February, to reach a “fair” agreement . “We regularly communicate with our stakeholders regarding labor issues and bargaining, and we’ve done so where we’ve received any letters from legislators,” an AT&T spokesman said.

The CWA says AT&T won’t negotiate over job security at call centers and retail stores where many of the employees work. “AT&T has increased its profits by cutting workers’ commissions, refused to bargain over job security even as it cut hundreds of call center jobs this year alone, and increasingly moved to low-wage contractors for its retail and call center operations,” Dennis Trainor, vice president for CWA district 1, said in a statement. “That’s not how America’s largest telecom should be acting.”

AT&T t has a long history of labor peace, though the May strike interrupted a run of more than four years without a walkout. The company says it has reached 32 agreements covering some 145,000 workers since the beginning of 2015. The strike in May, which also included 17,000 workers in AT&T’s telecom business, followed last year’s bitter, seven week strike at Verizonvz .